Selective electrochemical etching of p-CdTe (for photovoltaic cells)

Abstract

The electrochemical etching of p-CdTe is investigated. This etching is based on a method used previously for the selective etching of n-type Cd-chalcogenide semiconductors. We show that the electrochemical etching creates a dense pattern of submicron pits, and increases the reverse bias photocurrent of a Schottky barrier device, made up of single crystal p-CdTe and a polysulfide electrolyte typically by 20%. Evidence for the selective removal of surface defects is brought up and the conditions for selective etching are discussed in brief.

Porous Anodic Etching of p-Cd[sub 1−x]Zn[sub x]Te Studied by Photocurrent Spectroscopy

“…Anodization of other II-VI materials such as CdSe or CdS also leads to surface chemical films of undissolved oxidation products, and SeЊ or SЊ could have a similar effect as TeЊ on Cd 1Ϫx Zn x Te in favoring porous etching. It would be interesting to see whether anodization of other II-VI materials leads not only to superficial pitting as reported in the past [12][13][14][15][16][17][18][19][20][21] but also to the growth of thick porous layers as shown here with p-Cd 1Ϫx Zn x Te. The performances of photoelectrochemical solar cells based on II-VI materials are improved after anodic treatment, 19,62,63 and a question is whether porous etching could account for part of the changes.…”

“…Photocurrent of p-Cd 1Ϫx Zn x Te electrodes after porous etching.-A brief anodization causes a rise in ICPE, due to a decrease in surface reflectivity, as reported by Tenne. 19 Prolonged anodization causes a drop in ICPE, and the ICPE continues to drop, down to very low values, as long as anodic treatment is continued (see Fig. 6a).…”

“…Anodic treatment not only leads to a chemical surface film, but also to important changes in electrode morphology. Several reports indicate that anodization of II-VI semiconductors causes surface pitting, [12][13][14][15][16][17][18][19][20][21] but the authors do not address the question of whether pores extend deeply below the surface; their work focuses on surface roughening and its important effects on the photoelectrochemical properties. Recently, we showed that anodic treatment can render p-Cd 0.95 Zn 0.05 Te porous across a thickness of more than 100 m, 22 and nanoporous layers with quantum size effects have been obtained by anodization of p-ZnTe.…”

Electrochemical pore formation onto semiconductor surfaces

“…Porous etching of IIeVI materials was performed under illumination for n-type or in the dark for p-type materials. It was successively reported for n-CdSe [40], n-CdSe x Te 1Àx [41], n-CdS [42], n-CdTe [43], p-CdTe [44], p-Cd 1Àx Zn x Te [45], p-ZnTe [46]. Since improvement of the quantum efficiency was initially targeted by these studies, the layers were not described from the pore formation point of view.…”

Selective etching of ZnTe in HF:H2O2:H2O solution: Interpretation of extended defect‐related etch figures

“…Therefore, texturization etchants will also preferentially react with the atoms at and near the defects . Another advantage that makes the texturization etchants applicable for defect revealing is that, it can effectively remove the surface layer that contains contaminations and processing‐induced defects, thus can more precisely reveal the grown‐in defects .…”